An electrical connector assembly having a pair of mating electrical connectors mounted on a pair of boards, respectively, is well known and used to electrically interconnect the pair of boards. One or both of the pair of electrical connectors generally have a solder peg or solder pegs to secure bonding strength (mounting strength) to the boards. The solder peg not only secures bonding strength to the board, but also may have an electrically-conductive function for ground connection (see Japanese Patent No. JP 10-50371 A), or may function as a mating completion detecting switch (see Japanese Patent Application No. JP 2011-243332 A).
However, space is required to accommodate the solder peg in a housing of the electrical connector. In particular, if the solder pegs are provided in both of the pair of electrical connectors, downsizing is difficult.